The present invention relates to the field of manufacture of laminates, and more particularly relates to a method and a device for making a laminated plate, for example of a type which can be utilized as electrical insulation material.
In the prior art, for making a laminated plate such as a synthetic resin laminated plate, a suitable number of sheets of base material impregnated with thermosetting resin have been stacked together, and these sheets have then been laminated together, either by passing them between pressure rollers as exemplarily shown in a schematic side view in FIG. 1 of the accompanying drawings, or by pressing them in an open press as each being sandwiched between platens and pressed together, as exemplarily shown in a schematic frontal view in FIG. 2 of said accompanying drawings.
In more detail, in FIG. 1, the reference numeral 1 denotes sheets of a material such as for example stainless steel plate, aluminum foil, plastic film, or the like, which is used for protecting the material to be laminated during the lamination process, and the reference numeral 2 denotes a plurality of overlaid sheets of so called "prepreg" (this term will be used henceforward throughout this specification), which are to be laminated together. This prepreg may be made, for example, by impregnating natural or synthetic, organic or inorganic, woven or non woven fabric, cloth sheet material, such as paper, glass cloth, non woven glass cloth, asbestos cloth, polyester fiber cloth, or the like, with synthetic resin varnish or liquid synthetic resin such as phenol resin, epoxy resin, polyester resin, polyimide resin, silicon resin, or the like, and by then curing the synthetic resin into B-stage by heating/drying. The reference numeral 3 is used to denote each one of a plurality of heating and pressure rollers. Two sheets of the protective sheet material 1 are laid one on each side of a plurality of layers of the prepreg 2, and the thus formed sandwich of sheets of protective material 1 on either side of prepreg 2 is passed in sequence between a plurality of opposed pairs of these rollers 3 and is heated and compressed thereby, thus causing the prepregs 2 to be laminated together to form a laminated plate.
On the other hand, in the FIG. 2 apparatus, the reference numeral 4 is used to denote each of a plurality of platens which can be heated or cooled by a heating or cooling means incorporated therein, while 5 is an upper plate, 6 are support columns, 7 is a movable plate, 8 is a fixed base portion, 9 is a pressure piston, 10 is a pressure chamber, 11 is a hydraulic fluid inlet, and 12 is a hydraulic fluid outlet. The fixed base portion 8 supports the columns 6 to the tops of which the upper plate 5 is fixed, and the movable plate 7 is slidably mounted on the columns 6 and is selectively movable up and down said columns 6 by the operation of the hydraulic device constituted by the pressure piston 9 and the pressure chamber 10. When hydraulic fluid is supplied under pressure (from a pump and under the control of a control means which are not particularly shown in the figure) through the hydraulic fluid inlet 11 to the pressure chamber 10, then the pressure piston 9 is raised, thus raising the movable plate 7; but, on the other hand, when hydraulic fluid is drained through the hydraulic fluid outlet 12 from the pressure chamber 10, then the pressure piston 9 is lowered, thus lowering the movable plate 7. The uppermost one of the platens 4 is mounted to the lower surface of the upper plate 5, while the lowermost one of said platens 4 is mounted to the upper surface of the movable plate 7; and the other ones of said platens 4 are arranged in a vertically spaced and movable manner by a plurality of stoppers (not particularly shown in the drawing) between said upper plate 5 and said movable plate 7.
The material to be laminated, i.e. the prepreg, is cut into pieces of apporpriate size, and then an appropriate number of such sheets are pressed together between mirror plates, and a certain number (from a few to some tens) of such assemblies are combined together and are introduced between the platens 4, although this matter is not particularly shown in the figure. Then, as explained above, hydraulic fluid is supplied under pressure through the hydraulic fluid inlet 11 to the pressure chamber 10, and the pressure piston 9 and the movable plate 7 are raised towards the upper plate 5, thus squeezing together the platens 4 and the prepreg assemblies. At the same time, the platens 4 are heated; this maybe be done by forming said platens 4 with passages through which steam or the like is passed, but no such arrangements are particularly shown in the figures. Thus, the heat required for the compression molding and lamination is provided, and the prepreg sandwiches are heated and compressed, thus laminating them to form laminated plates.
In the case of the first one of these lamination processes as illustrated in FIG. 1, laminated plates of great length can be produced and the process can be operated continuously, but the process is applicable only to types of synthetic resin which require only a relatively short curing time by heat and pressure, since the laminate passes relatively quickly between each pair of rollers 3 and the whole area thereof is therefore not pressurized for a long time period. Since, however, most synthetic resins require at least several minutes of heating and pressuriziation for being molded and laminated, this first lamination process is not widely applicable nowadays, and rollers are usually only used for bonding laminate layers.
In the case of the second one of these lamination processes as illustrated in FIG. 2, high pressure and temperature can be applied over substantially the entire surface of the laminate for any desired time; but this type of flat press can only laminate sheets which are not larger than the press plates. Further, the process is a batch one. Accordingly, the productivity is not high.